November 14, 2012

Bioengineers from Harvard recently revealed that they have been able to develop injectable gel-based sponges that can deliver cells and drugs as well as be shaped into whatever size or form.

In particular, the sponge is able to revert back to its original shape once it has released whatever drugs or stem cells inside the body. Researchers believe that the item could be used for therapeutic purposes as a prefabricated healing kit.

“What we´ve created is a three-dimensional structure that you could use to influence the cells in the tissue surrounding it and perhaps promote tissue formation,” noted principal investigator David J. Mooney, a professor of bioengineering at the Harvard School of Engineering and Applied Sciences (SEAS) and a Core Faculty Member at the Wyss Institute for Biologically Inspired Engineering at Harvard, in a prepared statement.

Using the injectable sponge, the researchers were able to show how live cells can be delivered intact with the use of a small-bore needle. The sponge, made up of seaweed-based jelly alginate, could also contain large and small proteins or drugs. These drugs and proteins would be late released to help take apart mechanisms in the body. The sponge was useful, with no need to be implanted surgically.

“The simplest application is when you want bulking,” continued Mooney in the statement. “If you want to introduce some material into the body to replace tissue that´s been lost or that is deficient, this would be ideal. In other situations, you could use it to transplant stem cells if you´re trying to promote tissue regeneration, or you might want to transplant immune cells, if you´re looking at immunotherapy.”

In order to develop the sponge, the researchers used cyrogelation, a freezing process that forms pure ice crystals following the freezing of water in the alginate solution. When the ice crystals melt, there is a set of pores and, if done correctly, a strong and compressible gel forms. With these various facets, the “cryogel” is considered unique in the biomedical engineering field.

“These injectable cryogels will be especially useful for a number of clinical applications including cell therapy, tissue engineering, dermal filler in cosmetics, drug delivery, and scaffold-based immunotherapy,” commented the study´s lead author Sidi Bencherif, a postdoctoral research associate in Mooney´s lab at SEAS and at the Wyss Institute, in the statement. “Furthermore, the ability of these materials to reassume specific, pre-defined shapes after injection is likely to be useful in applications such as tissue patches where one desires a patch of a specific size and shape, and when one desires to fill a large defect site with multiple smaller objects. These could pack in such a manner to leave voids that enhance diffusion transport to and from the objects and the host, and promote vascularization around each object.”

In moving forward with the project, the researchers are planning to experiment with the degradation rate of the bioscaffold. They are interested in having the sponge break into pieces at the same rate as the growth and replacement of new tissue. Having filed a patent application of the device, Harvard´s Office of Technology is looking into commercialization and licensing options.

The findings on this new biocompatible technology was recently published in the Proceedings of the National Academy of Sciences (PNAS).

Image 2 (below): Left: A fully collapsed square-shaped cryogel rapidly regains its original memorized shape, size, and volume upon hydration. Right: Photos show the placement of a cryogel inside a 1-mL syringe, and the recovery of a square gel after injection through a normal 16-gauge needle. Images courtesy of Sidi Bencherif.